In the United States, millions of units of donated whole blood are collected by blood banks each year. Whole blood is made up of red blood cells, white blood cells (also called leukocytes), and platelets, all suspended in a protein-containing fluid called plasma. Because patients are not likely to require each component of whole blood, most of the whole blood collected from donors is not stored and used for transfusion. Instead, the whole blood is separated into its clinically therapeutic components, red blood cells, platelets and plasma. The components are stored individually and used to treat a multiplicity of specific conditions.
A number of fluid separation devices have been known and various models are currently available for the separation of whole blood or other composite fluids into the various component elements thereof. For example, a variety of centrifugal machines are available for separating blood into component elements such as red blood cells, platelets and plasma, inter alia.
Centrifugation in the past has been used for separation in many forms in both continuous and batch types. For example, in the widely used process known as continuous centrifugation, as generally opposed to batch process centrifugation, a continuous input of a composite fluid is flowed into the separation device or chamber while at the same time the components of that composite fluid are substantially continuously separated and these continuously separating components are usually then also substantially continuously removed therefrom. Many currently popular forms of such continuous fluid separation devices include loops of entry and exit flow tubing lines connected to the separation centrifuge chamber such that each loop is rotated in a relative one-omega-two-omega (1ω-2ω) relationship to the centrifuge chamber itself so that the tubing lines will remain free from twisting about themselves.
An alternative form of tubing line connection to a continuous centrifugal separation device is also available in the art which does not have such a loop, but which instead requires one or more rotating seals at the respective connections of the tubing lines to the centrifuge separation chamber, again to maintain the tubing lines free from twisting.
Batch-type centrifugation, on the other hand, usually involves separation of a composite fluid such as whole blood in a closed container, often a deformable bag, followed by removal of the container/bag from the separation device and then subjecting the container/bag to a relatively difficult process of automated and/or manual expression of one or more of the separated components out of the separation container or bag. A great deal of control, either automated, such as by optical interface detection, or by a diligent human operator watching a moving interface, is required with such previous batch-type processes.
One type of known batch-type centrifuge uses buckets for holding bags of, for example, whole blood collected from a donor. The buckets rotate to separate the components inside the bags. The bags are then removed from the centrifuge where they are expressed by an operator using a manual expressor to remove components from the bag. Another type of centrifugal apparatus that also functions as a cell washer is the COBE 2991 system available from Gambro BCT, Inc., Lakewood, Colo. The COBE 2991 as well as PCT International Publication No. WO01/97943 and U.S. Pat. No. 6,315,706 use an expressor fluid or hydraulic fluid for removing separated components.
Indeed, various means and methods have been used in or with prior centrifugal separation systems, both continuous and batch, for driving fluid flow and maintaining desirable interface position control between the component elements being separated thereby. For example, as mentioned, various optical feedback methods and devices have been employed in the art. Various pumping and valving arrangements have also been used in various of these and other arrangements. Alternative relatively automatic volume flow and density relationship interface controls have also been used; for example, in a continuous system by the disposition of control outlet ports in strategic locations relative to the separated component outlet ports.
Nevertheless, many facets of these prior separation devices, though providing heretofore satisfactory production, may yield certain features which are less efficient than a desired optimum. For example, for collecting random donor platelets from whole blood it was necessary to have a second spin and tighter control over the interface between components which in the past was difficult with a manual expressor. Another disadvantage of prior art systems is that frequently the interface was required to move. For example, in hand or manual expression, the interface moves during the component removal process. This can result in difficulties in maintaining the desired interface for optimum collection.
Hence, substantial desiderata remain to provide a more highly efficient centrifugal separation device particularly for whole blood in terms of increased efficiency fluid flow drive and separation interface controls; and/or reduced seal need and/or intricacy. It is toward any one or more of these or other goals as may be apparent throughout this specification that the present invention is directed.